1,498 research outputs found
Higher physical fitness levels are associated with less language decline in healthy ageing
Healthy ageing is associated with decline in cognitive abilities such as
language. Aerobic fitness has been shown to ameliorate decline in some
cognitive domains, but the potential benefits for language have not been
examined. In a cross-sectional sample, we investigated the relationship between
aerobic fitness and tip-of-the-tongue states. These are among the most frequent
cognitive failures in healthy older adults and occur when a speaker knows a
word but is unable to produce it. We found that healthy older adults indeed
experience more tip-of-the-tongue states than young adults. Importantly, higher
aerobic fitness levels decrease the probability of experiencing
tip-of-the-tongue states in healthy older adults. Fitness-related differences
in word finding abilities are observed over and above effects of age. This is
the first demonstration of a link between aerobic fitness and language
functioning in healthy older adults
The Clusters AgeS Experiment (CASE). II. The Eclipsing Blue Straggler OGLEGC-228 in the Globular Cluster 47 Tuc
We use photometric and spectroscopic observations of the eclipsing binary
OGLEGC-228 (V228) to derive the masses, radii, and luminosities of the
component stars. Based on measured systemic velocity, proper motion and
distance, the system is a blue straggler member of the globular cluster 47 Tuc.
Our analysis shows that V228 is a semi-detached Algol. We obtain M=1.512 +/-
0.022 Msun, R=1.357 +/- 0.019 Rsun, L=7.02 +/- 0.050 Lsun for the hotter and
more luminous primary component and M=0.200 +/- 0.007 Msun, R=1.238 +/- 0.013
Rsun, L=1.57 +/- 0.09 Lsun for the Roche lobe filling secondary.Comment: 19 pages, 5 figures, AJ, in pres
Influence of extended dynamics on phase transitions in a driven lattice gas
Monte Carlo simulations and dynamical mean-field approximations are performed
to study the phase transition in a driven lattice gas with nearest-neighbor
exclusion on a square lattice. A slight extension of the microscopic dynamics
with allowing the next-nearest-neighbor hops results in dramatic changes.
Instead of the phase separation into high- and low-density regions in the
stationary state the system exhibits a continuous transition belonging to the
Ising universality class for any driving. The relevant features of phase
diagram are reproduced by an improved mean-field analysis.Comment: 3 pages, 3 figure
Variational method and duality in the 2D square Potts model
The ferromagnetic q-state Potts model on a square lattice is analyzed, for
q>4, through an elaborate version of the operatorial variational method. In the
variational approach proposed in the paper, the duality relations are exactly
satisfied, involving at a more fundamental level, a duality relationship
between variational parameters. Besides some exact predictions, the approach is
very effective in the numerical estimates over the whole range of temperature
and can be systematically improved.Comment: 20 pages, 5 EPS figure
Palette-colouring: a belief-propagation approach
We consider a variation of the prototype combinatorial-optimisation problem
known as graph-colouring. Our optimisation goal is to colour the vertices of a
graph with a fixed number of colours, in a way to maximise the number of
different colours present in the set of nearest neighbours of each given
vertex. This problem, which we pictorially call "palette-colouring", has been
recently addressed as a basic example of problem arising in the context of
distributed data storage. Even though it has not been proved to be NP complete,
random search algorithms find the problem hard to solve. Heuristics based on a
naive belief propagation algorithm are observed to work quite well in certain
conditions. In this paper, we build upon the mentioned result, working out the
correct belief propagation algorithm, which needs to take into account the
many-body nature of the constraints present in this problem. This method
improves the naive belief propagation approach, at the cost of increased
computational effort. We also investigate the emergence of a satisfiable to
unsatisfiable "phase transition" as a function of the vertex mean degree, for
different ensembles of sparse random graphs in the large size ("thermodynamic")
limit.Comment: 22 pages, 7 figure
The RCSB Protein Data Bank: views of structural biology for basic and applied research and education.
The RCSB Protein Data Bank (RCSB PDB, http://www.rcsb.org) provides access to 3D structures of biological macromolecules and is one of the leading resources in biology and biomedicine worldwide. Our efforts over the past 2 years focused on enabling a deeper understanding of structural biology and providing new structural views of biology that support both basic and applied research and education. Herein, we describe recently introduced data annotations including integration with external biological resources, such as gene and drug databases, new visualization tools and improved support for the mobile web. We also describe access to data files, web services and open access software components to enable software developers to more effectively mine the PDB archive and related annotations. Our efforts are aimed at expanding the role of 3D structure in understanding biology and medicine
Effects of finite curvature on soliton dynamics in a chain of nonlinear oscillators
We consider a curved chain of nonlinear oscillators and show that the
interplay of curvature and nonlinearity leads to a number of qualitative
effects. In particular, the energy of nonlinear localized excitations centered
on the bending decreases when curvature increases, i.e. bending manifests
itself as a trap for excitations. Moreover, the potential of this trap is
double-well, thus leading to a symmetry breaking phenomenon: a symmetric
stationary state may become unstable and transform into an energetically
favorable asymmetric stationary state. The essentials of symmetry breaking are
examined analytically for a simplified model. We also demonstrate a threshold
character of the scattering process, i.e. transmission, trapping, or reflection
of the moving nonlinear excitation passing through the bending.Comment: 13 pages (LaTeX) with 10 figures (EPS
Density functional theory for nearest-neighbor exclusion lattice gasses in two and three dimensions
To speak about fundamental measure theory obliges to mention dimensional
crossover. This feature, inherent to the systems themselves, was incorporated
in the theory almost from the beginning. Although at first it was thought to be
a consistency check for the theory, it rapidly became its fundamental pillar,
thus becoming the only density functional theory which possesses such a
property. It is straightforward that dimensional crossover connects, for
instance, the parallel hard cube system (three-dimensional) with that of
squares (two-dimensional) and rods (one-dimensional). We show here that there
are many more connections which can be established in this way. Through them we
deduce from the functional for parallel hard (hyper)cubes in the simple
(hyper)cubic lattice the corresponding functionals for the nearest-neighbor
exclusion lattice gases in the square, triangular, simple cubic, face-centered
cubic, and body-centered cubic lattices. As an application, the bulk phase
diagram for all these systems is obtained.Comment: 13 pages, 13 figures; needs revtex
Including a pen and/or cover letter, containing social incentive text, had no effect on questionnaire response rate : a factorial randomised controlled Study within a Trial [version 1; peer review: awaiting peer review]
Background: Postal questionnaires are frequently used in randomised controlled trials to collect outcome data on participants; however, poor response can introduce bias, affect generalisability and validity, and reduce statistical power. The objective of this study was to assess whether a pen and/or social incentive text cover letter sent with a postal follow-up questionnaire increased response rates in a trial. Method: A two-by-two factorial randomised controlled trial was embedded within the OTIS host trial. Participants due their 12-month (final) follow-up questionnaire were randomised to be sent: a pen; a social incentive text cover letter; both; or neither. The primary outcome measure was the proportion of participants in each group who returned the questionnaire. Secondary outcomes were: time to return, completeness of the questionnaire, necessity of a reminder letter, and the cost effectiveness. Results: The overall 12-month questionnaire response rate was 721 out of 755 (95.5%). Neither the pen nor social incentive cover letter had a statistically significant effect on response rate: pen 95.2% vs. no pen 95.8%, adjusted OR 0.90 (95% CI 0.45 to 1.80; p=0.77); social incentive cover letter 95.2% vs. no social incentive cover letter 95.8%, adjusted OR 0.84 (95% CI 0.42 to 1.69, p=0.63). No statistically significant differences were observed between either of the intervention groups on time to response, need for a reminder or completeness. Therefore, neither intervention was cost-effective. Conclusions: We found no evidence of a difference in response rates associated with the inclusion of a pen and/or social incentive cover letter with the final follow-up postal questionnaire of the host trial. However, when these results are combined with previous SWATs, the meta-analysis evidence remains that including a pen increases response rates. The social incentive cover letter warrants further investigation to determine effectiveness
Performance of the double multilayer monochromator on the NSLS wiggler beam line X25
A tunable, double multilayer x-ray monochromator has recently been implemented on the National Synchrotron Light Source (NSLS) X25 wiggler beam line. It is based on a parallel pair of tungsten-boron-carbide multilayer films grown on silicon substrates and purchased from Osmic, Inc. of Troy, Michigan, USA. It acts as an optional alternative to the conventional double silicon crystal monochromator, and uses the same alignment mechanism. Two other NSLS beam lines also have had this kind of monochromator installed recently, following the lead of the NSLS X20C IBM/MIT beam line which has used a double multilayer monochromator for several years. Owing to the 100 times broader bandwidth of a multilayer x-ray monochromator, compared with a silicon monochromator, the multilayer monochromator has the obvious advantage of delivering 100 times the flux of a silicon monochromator, and thereby makes more efficient use of the continuous synchrotron radiation spectrum, yet preserves the narrow collimation of the incident synchrotron beam. In particular, multilayer x-ray bandwidths, on the order of 1%, are well-matched to x-ray undulator linewidths. Performance results for the X25 multilayer monochromator are presented, comparing it with the silicon monochromator. Of note is its short- and long-term performance as an x-ray monochromator delivering the brightness of the wiggler source in the presence of the high-power white beam. Detailed measurements of its spatial beam profile and wavelength dispersion have been made, and it is shown how its resolution could be improved when desired. Finally, its peculiar, anisotropic resolution function in reciprocal space, and its bearing upon x-ray crystallography and scattering experiments, will be discussed, and highlighted by the results of a protein crystallography experiment. © 1997 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87844/2/71_1.pd
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